Some display devices require a backlight unit for generating light to display images. The backlight unit is a device for supplying the light to a display panel including liquid crystal and includes a light emitting device and means for effectively transferring the light emitted from the light emitting device to the liquid crystal.
A light emitting diode (LED) can be used as a light source for the display device. In addition, a light guide plate and optical sheets may be laminated in the display device to effectively transfer the light generated from the light source to the display panel.
An optical member that converts the wavelength of the light generated from the light source such that white light can be incident into the light guide plate or the display panel can be employed in the display device. In particular, quantum dots may be used to convert the wavelength of the light.
The quantum dot has a particle size of 10 nm or less and the electric and optical characteristics of the quantum dot may vary depending on the particle size thereof. For instance, if the quantum dot has the particle size in the range of about 55 Å to about 65 Å, light having a red color can be emitted. In addition, if the quantum dot has the particle size in the range of about 40 Å to about 50 Å, light having a green color can be emitted and if the quantum dot has the particle size in the range of about 20 Å to about 35 Å, light having a blue color can be emitted. The quantum dot emitting light having a yellow color may have the intermediate particle size between the particle sizes of the quantum dots emitting the red and green colors. The color of the spectrum according to the wavelength of the light tends to be shifted from the red color to the blue color, so it is estimated that the size of the quantum dot may be sequentially changed from 65 Å to 20 Å and this numerical values may be slightly changed.
In order to form the optical member including the quantum dots, the quantum dots emitting RGB colors, which are the three primary colors of the light, or RYGB colors are spin-coated or printed on a transparent substrate, such as a glass substrate. If the quantum dot emitting the yellow color is added, the white light approximate to natural light can be obtained. A matrix (medium) which disperses and carries the quantum dots may emit the light having the visible ray band and the ultraviolet ray band (including far UV band) and may employ an inorganic substance or a polymer representing superior transmittance for the light having the visible ray band. For instance, the organic substance or the polymer may include inorganic silica, polymethylmethacrylate (PMMA), polydimethylsiloxane (PDMS), poly lactic acid (PLA), silicon polymer or YAG.
A display device employing such a quantum dot is disclosed in Korean Unexamined Patent Publication No. 10-2011-0012246.